Suture rings of the type specified above are widely known in the art.
These suture rings are usually covered (and, in some cases, constituted entirely) by fabrics made of biocompatible synthetic materials which are intended to form a woven structure through which surgical stitches can be inserted to suture the prosthesis in its implant position after the removal of the natural valve flaps.
Conflicting requirements must generally be taken into account in the selection of these materials.
On the one hand, it is desirable for the suture ring not to absorb blood or cause any appreciable resistance to the blood flow which might have a haemolytic or thrombogenic effect. This means that the selection of the covering material is oriented towards substantially water-repellent materials such as polytetrafluoroethylene (also known by the trade name of Teflon).
The use of these materials, however, conflicts with the need for the external region of the suture ring, which is exposed to the sutured tissue, to be colonized by that tissue so that, in time, the prosthesis becomes firmly anchored in its implant position.
This latter requirement could be satisfied very well with the use of substantially hydrophilic, porous materials such as, for example, polyethylene terephthalate (also known by the trade name of Dacron). These materials in turn are somewhat prone to absorbing blood and may also have a considerable haemolytic effect on the mass of blood to which the suture ring is exposed during use.
The object of the present invention is to provide a suture ring for heart valve prostheses in which the aforesaid requirements can be satisfied simultaneously without giving rise to the problems described.